This invention relates to a computer mouse with an improved ball lock.
A computer mouse is widely used as a pointing device with personal computers. A common form of computer mouse comprises a housing for gripping in the user's hand and sliding over a mouse pad. The housing has a bottom wall that confronts the mouse pad. The bottom wall of the housing is formed with a recess that contains a removable retainer plate or ball lock. The retainer plate is formed with a circular hole which is somewhat smaller than the diameter of a mouse ball that is located inside the housing and allows the mouse ball to protrude from the housing while remaining captive within the housing. When the retainer plate is removed, the mouse ball can be removed from the housing.
The conventional retainer plate is coupled to the bottom wall of the housing using a bayonet-type coupling. The retainer plate includes bayonet coupling lugs and corresponding slots are formed in the base of the recess in the bottom wall of the housing. The retainer plate is engaged with the bottom wall of the housing by placing the plate in the recess, with the bayonet coupling lugs in the slots respectively, and then rotating the plate through about 45.degree. in the clockwise direction. Similarly, the retainer plate can be disengaged by rotating the retainer plate through an angle of about 45.degree. in the counterclockwise direction.
The ease with which the retainer plate can be disengaged from the bottom wall of the housing is advantageous because it allows the mouse ball to be removed for cleaning without need for special tools. However, in some respects this feature can also be a disadvantage, particularly when applied to a computer mouse that is used in a school, because if the mouse ball can be easily removed for cleaning by a teacher or technician, it can also be easily removed by a curious or bored student whose plans do not include cleaning and replacing the mouse ball. If unauthorized removal of a mouse ball is not detected by a teacher or other person having reason to ensure that the mouse ball is promptly replaced, the ball might be misplaced and it might then be necessary to obtain either a new mouse ball or replace the entire mouse.
U.S. Pat. No. 5,610,532 and U.S. Pat. No. 5,668,575 each disclose a seal for resisting removal of the retainer plate from the opening in the bottom wall.
U.S. Pat. No. 5,867,147 discloses a mouse in which the retainer plate is configured so that it is essentially free of gripping surfaces that would facilitate removal of the disk by human fingers and has sockets which can be engaged by a special tool to allow authorized personnel to remove the retainer plate.